I am an Assistant Professor of Economics at the National University of Singapore. I work on environmental economics, applied micro, and the digital economy. 

I received my Ph.D. from the Sustainable Development program at Columbia University in 2023.

CV (September 2023)

Email: xdu@nus.edu.sg

Job market paper:

Columbia CEEP WP 24, CESifo WP 10296

This paper provides the first causal evidence that hostile activities online cause physical violence. Given the recently documented relationship between pollution and social media, I exploit exogenous variation in local air quality as an instrument for online aggression. An event study analysis shows air pollution increases by 7% when refineries experience unexpected malfunctions. On days with pollution spikes, surrounding areas see 30% more aggressive tweets and 12% more crimes; geographically distant but socially networked regions also see aggressive tweets increase by 3% and crimes by 4.5%. My findings highlight the impacts of social media hostility and contribute to the public debate on cyberspace regulation.

Working papers:

Columbia CEEP WP 26, Old version May 2022 (chapter three)

This paper studies the short-term trade-off between economic growth and environmental governance from the perspective of political incentives. In the context of international trade conflicts, we use the U.S.-China trade war as a natural experiment and find that higher U.S. tariffs worsen air quality in China. The city-level analysis shows that a 1% increase in the tariff burden leads to 0.9% and 0.7% increases in SO2 and PM2.5, respectively.  Firm-level emission data generate similar results. Interestingly, the hourly monitor-level air quality data suggests that the pollution increases are concentrated at night. We hypothesize that the surprising findings can be largely attributed to the lenient environmental policies adopted by local governments when faced with the risks of economic downturn. We provide suggestive evidence that cities more exposed to the U.S. tariffs attach less emphasis on environmental regulations in local government reports and charge fewer fines on firms violating environmental regulations. Cities with native and older party secretaries and areas closer to province boundaries experience a less severe increase in pollution during the trade war. Our findings are relevant as China scrambles to maintain growth in the face of economic headwinds.



Schedule an appointment: https://calendly.com/xd2197/office-hours

EC2383 Environmental Economics

EC4305 Applied Econometrics